1. Technical Field
The present invention relates to liquid ejecting apparatuses, and particularly relates to a configuration for a liquid flow channel that supplies a liquid to a liquid ejecting head.
2. Related Art
Generally, ink jet printers have been widely known for some time as one type of liquid ejecting apparatus that ejects a liquid onto a medium. Such printers carry out printing by ejecting ink (a liquid) supplied from an ink cartridge (a liquid supply source) from an ejecting nozzle formed in a liquid ejecting head onto a medium (for example, paper). Recently, pigment inks are being used in such printers in order to realize high-image quality printing.
Pigment inks have a problem in that the pigment particles sink in the ink carrier as time passes, resulting in imbalances in the concentration of the pigment ink, which in turn leads to changes in the tint. It is particularly easy for pigment particles to sink within a liquid flow channel from the ink cartridge to the liquid ejecting head in the case where the liquid flow channel is long. Accordingly, even if agitated ink is supplied to the liquid flow channel from the ink cartridge, it is difficult to suppress changes in the tint of the pigment ink unless imbalances in the concentration of the pigment ink are suppressed in the liquid flow channel between the ink cartridge and the liquid ejecting head.
Accordingly, JP-A-2011-255643, for example, proposes a technique for agitating ink in a liquid flow channel. This technique is a technique for instigating ink flow within a liquid flow channel and agitating the ink by using a tube pump in which rollers rotate while squeezing a flexible tube in order to produce pressure fluctuations within a circulating flow channel that configures part of the liquid flow channel.
Incidentally, in printers, a check valve is normally provided between the liquid supply source and the circulating flow channel to ensure that the ink does not flow in reverse from the liquid flow channel toward the liquid supply source. Accordingly, in the case where ink is caused to flow through a circulating flow channel using pressure fluctuations that are repeatedly produced by a tube pump as disclosed in JP-A-2011-255643, the ink will flow into the circulating flow channel from the liquid supply source side via the check valve when the pressure fluctuations cause a drop in the pressure within the circulating flow channel near the check valve. A phenomenon will then occur in which the ink that has flowed into the circulating flow channel will not return toward the liquid supply source due to the effect of the check valve, even after the drop in the pressure within the circulating flow channel near the check valve has been eliminated.
Accordingly, if the tube pump is driven for a long period of time, the ink will repeatedly flow into the circulating flow channel from a liquid holding member as a result of the repeated drops in the pressure, leading to a gradual increase in the amount of ink within the circulating flow channel; this in turn will cause the pressure of the ink within the circulating flow channel to rise. As a result, in the case where the circulating flow channel (liquid flow channel) is formed by connecting a plurality of tubes, the connections between the tubes can become disengaged, the tubes can rupture, or the like.
Note that the situation is not limited to ink jet printers, and has generally been common in any liquid ejecting apparatus that supplies a liquid to an ejection mechanism from a liquid supply source via a liquid flow channel in which a check valve is provided and that ejects the stated liquid through the ejection mechanism.